1. Field of the Invention
The present invention relates to improvements in rotary sleeve bearing apparatus for a rotary compressor which is utilizable as a supercharger for an internal combustion engine and provided with a rotary sleeve mounted in a center housing for rotation with a plurality of vanes movable in a rotor which is eccentrically disposed in the rotary sleeve.
2. Description of the Prior Art
A movable vane compressor of the type having a rotary sleeve supported by compressible fluid such as air is utilizable as a supercharger for an automobile engine required to run over a wide speed range. The rotary sleeve rotates together with a plurality of vanes to prevent frictional heat and wear at the apex of each vane. And yet it has the possibility of scuffing and seizure troubles if air is highly compressed in the compression working space confined among the rotary sleeve, the rotor and the adjacent vanes to push the rotary sleeve from within to the inner periphery of the center housing. In Japanese Patent Application Serial Number Sho 58-28608, the inventors of this application have proposed to supply air to an air-bearing room between the inner periphery of the center housing and the outer periphery of the rotary sleeve through an inlet which is internally connected to one of the discharge chamber, the compression working space under the maximum pressure, or the open air. The supplied air increases the flowing of air along an area of the compression side inner periphery of the center housing to protect scuffing between the rotary sleeve and the center housing. It is desirable for the air-bearing room to be supplied with the high-pressure air in the compression working space or discharge chamber. However, the supplied air has a pulsating pressure which results from a cyclical change of the compression ratio in the compression working space causing pulsation of air both in the compression working space and in the discharge chamber internally connected thereto. The pulsation in the air supplied into the air-bearing room may vibrate the rotary sleeve. Especially, in high-speed and high-load operations, the pulsation not only causes the rotary sleeve to contact the inner periphery of the center housing but also the vane to vibrate against the inner periphery of the rotary sleeve with the result that scuffing between the rotary sleeve with the center housing and wearing between the rotary sleeve and the vanes. Another problem is that, as the temperature rises in the discharge chamber or compression working space, the air supplied to the air-bearing room is insufficient in density to increase the bearing performance of the air-bearing room.
It is the primary object of the present invention to provide a rotary-sleeve bearing apparatus for a rotary compressor in which the air-bearing effect is less affected by the pulsation and temperature of the air which is extracted from the discharge chamber or compression working space and supplied to the air-bearing room.